1. Field of the Invention
The present invention relates to an organic light emitting element including an anode, a cathode, and a layer containing an organic compound (hereinafter, referred to as an electroluminescent layer) that generates light by applying an electric field through itself; and a light emitting device including the light emitting element. Specifically, the present invention relates to an organic light emitting element that exhibits white light emission and a full color light emitting device including the white light emitting element.
As used herein, the term “light emitting device” refers to an image display device or a light source (including a lighting system). Further, a module having a light emitting element attached with a connector such as an FPC (Flexible Printed Circuit), a TAB (Tape Automated Bonding), or a TCP (Tape Carrier Package); a module having a TAB or a TCP provided with a printed wiring board at the tip thereof; and a module having a light emitting element directly mounted with an IC (Integrated Circuit) by COG (Chip On Glass) are all included in the light emitting device.
2. Related Art
An electroluminescent element includes an electroluminescent layer interposed between a pair of electrodes (anode and cathode). The emission mechanism is as follows. Upon applying a voltage between the pair of electrodes, holes injected from the anode and electrons injected from the cathode are recombined with each other at luminescent centers within the electroluminescent layer to lead to formation of molecular excitons, and the molecular excitons return to the ground state while radiating energy to emit photon.
An electroluminescent layer in the electroluminescent element may be made of low molecular weight materials or high molecular weight materials by vapor deposition (including vacuum vapor deposition), spin application, ink jetting, dipping, electrolytic polymerization, or the like.
These methods are appropriately selected depending on properties of materials or a shape of a film. For example, electrolytic polymerization is used to pattern form a film made of high molecular weight materials. (For example, refer to Japanese Unexamined Patent Publication No. 9-97679.)
A light emitting element containing an organic compound has a defect to be easily deteriorated by various factors; therefore, it is the biggest issue to obtain high reliability (longer lifetime) of the light emitting element.
The light emitting element containing an organic compound is easily deteriorated, and a defective condition in which a partial decrease in luminance occurs or a non-light-emitting region is generated is observed. When a layer containing an organic compound is crystallized, characteristics (luminance-current characteristics, current efficiency-current characteristics, current-voltage characteristics, or the like) are deteriorated.